Transition detector circuits may be used to monitor timing and critical paths of applications such as on-chip logic. Transition detectors may detect a transition in a data signal relative to a clock signal. For example a transition detector may detect whether a transition occurs within a window relative to the clock signal, and may be applicable to circuits where timing errors due to a data transition occurring too close to a clock edge may be identified and corrected.
Various implementations of transition detectors exist. For example, IEEE Journal January 2011, “A Power Efficient 32 Bit ARM Processor Using Timing-Error Detection and Correction for Transient-Error Tolerance and Adaptation to PVT Variation” Bull D., Das S., Shivashankar K., Dasika G., Flauntner K, Blaauw D., which is incorporated herein by reference, describes an example of a transition detector having two different pulse-generating parts for detecting a data-rise and a data-fall transition of a signal.
ICICDT 08 IEEE Conference “Energy-Efficient and Metastability-Immune Timing-Error Detection and Recovery Circuits for Dynamic Variation Tolerance”, Bowman K., Tschanz J., Kim N., Lee J., Wilkerson C., Lu S., Karnik T., De V., which is incorporated herein by reference, describes a transition detector implemented using latches and having an error-retaining circuit.
25th IEEE VLSI Test Symposium “Circuit Failure Prediction and Its Application to Transition Ageing”, Mitra S., Zhang M., Paul B., Agarwal M., which is incorporated herein by reference, describes a transition detector having two latches with a delayed input into the second latch and comparing the outputs of both latches for differences between the signals.
Due to the sensitive timing issues that are dealt with by transition detectors, some transition detectors may have contention issues within their design and/or operation. Some transition detectors incorporating a level-sensitive approach may miss transitions and may, therefore, not be suitable for circuits that are sensitive to error.
Furthermore, a physical implementation of a transition detector may lead to errors within the functioning of the transition detector due to physical factors such as operational parameters and global and local variations.